1. Field of the Invention
The present invention relates to a power supply apparatus, and especially relates to a power supply apparatus with an auxiliary boost circuit.
2. Description of the Related Art
FIG. 1 shows a block diagram of a related art power supply apparatus. A related art power supply apparatus 40 is applied to an alternating current power supply apparatus 20 and a load apparatus 30. The related art power supply apparatus 40 includes a rectification circuit 102, a power factor correction circuit 104 and a direct current to direct current conversion circuit 108.
The rectification circuit 102 is electrically connected to the alternating current power supply apparatus 20. The power factor correction circuit 104 is electrically connected to the rectification circuit 102. The direct current to direct current conversion circuit 108 is electrically connected to the power factor correction circuit 104 and the load apparatus 30.
The alternating current power supply apparatus 20 sends an alternating current power 22 to the rectification circuit 102. The rectification circuit 102 rectifies the alternating current power 22 to obtain a direct current power 24. The rectification circuit 102 sends the direct current power 24 to the power factor correction circuit 104. The power factor correction circuit 104 processes the direct current power 24 to obtain a power factor correction power 26.
The power factor correction circuit 104 sends the power factor correction power 26 to the direct current to direct current conversion circuit 108. The direct current to direct current conversion circuit 108 converts the power factor correction power 26 into a driving power 29. The direct current to direct current conversion circuit 108 sends the driving power 29 to the load apparatus 30.
FIG. 2 shows a voltage waveform diagram of an embodiment of the power factor correction power of the related art power supply apparatus. Please refer to FIG. 1 as well. The power factor correction power 26 is a 400 volts direct current power when the alternating current power supply apparatus 20 supplies the alternating current power 22 normally.
The power factor correction power 26 will not drop to zero immediately when the alternating current power supply apparatus 20 stops supplying the alternating current power 22 (dotted line). The power factor correction power 26 will drop to zero gradually, so that the direct current to direct current conversion circuit 108 and the load apparatus 30 are protected. A hold up time (for example, 10 milliseconds) is defined as a time interval between the alternating current power supply apparatus 20 stopping supplying the alternating current power 22 and the power factor correction power 26 becoming zero.
The direct current to direct current conversion circuit 108 is still possibly damaged by the variation of the power factor correction power 26 although the power factor correction power 26 drops to zero gradually when the alternating current power supply apparatus 20 stops supplying the alternating current power 22. Therefore, the components of the direct current to direct current conversion circuit 108 must have high specifications (for example, high voltage resistance). The cost of the direct current to direct current conversion circuit 108 is increased.